1. Field of the Invention
This invention relates to pumps and pumping apparatus. More particularly, the present invention relates to pumps for transporting slurries and other abrasive containing fluids in the use of centrifugal pumps. The invention is particularly concerned with controlling the effect of the inherent wear that is characteristic for centrifugal pumps used for transporting slurries and abrasive-containing fluids.
2. The Prior Art
Slurry pumps are used in many fields such as dredging waterways, transportation of fluidized solids and the like. Such pumps also have been used for many years and typically include an impeller that is designed with a nose formed by a radial projection facing towards the suction side of the pump and extending a short distance radially outwardly from the axis of the impeller. This impeller nose is provided with a nose surface that is perpendicular to the axis of the impeller and confronts a complementary surface that is integral with the suction liner formed as a separate part of the housing of the pump. There must be a clearance referred to in the art as the "impeller nose clearance" between the impeller nose surface and the confronting suction liner surface. This nose clearance or gap is typically specified by the manufacturer of the pump and may vary in accordance with the size of the pump, however, usually is in the range of about 1/32 of an inch when the pump is new. When the pump is used to transport the slurries and other solid-containing liquids, the abrasive conditions wear the confronting surfaces to such an extent that the impeller nose clearance increases dramatically causing a loss of efficiency due to the slurry not being controlled by the action of the impeller, and as the nose clearance becomes greater, more of the slurry and abrasive-containing liquid passes through the gap causing even greater wear and increasing the gap substantially to the point that the pump becomes inefficient and ineffective. At the time that such a drop in efficiency is noted, the pump must be stopped, thus ceasing the pumping operations of the liquid slurry and the pump must be dismantled and either or both the impeller or suction liner being replaced. This procedure is an expensive and time-consuming operation primarily for the reason that the pumping operation must cease during the period of correcting the oversized gap.
The prior art pumps had an integral construction of the suction liner with the portion forming the nose clearance with the impeller nose. Thus, simple adjustments to correct the nose clearance were not possible and the costly and uneconomical shutdowns could not be averted.